Methods and apparatuses for delivering a volatile component via a controlled exothermic reaction

ABSTRACT

Reaction mixtures that include exothermic generating particles having a water soluble coating encasing a portion of the particles, a volatile component and, optionally an aqueous solution, and a buffer. The reaction mixtures are especially suited to generate heat in a controllable manner. In one such controlled reaction, the reaction components are mixed together and the mixture increases in temperature to a Set Temperature within a predetermined time, and the mixture remains at the Set Temperature for a longer period of time. In this manner, volatile components can be controllably released to the surrounding environment. The volatile components can be, for example, a perfume, a fragrance, an insect repellent, a fumigant, a disinfectant, a bactericide, an insecticide, a pesticide, a germicide, an acaricide, a sterilizer, a deodorizer, a fogging agent and mixtures of these. Apparatuses and methods that use these reaction mixtures are also disclosed.

CROSS REFERENCE TO PRIOR APPLICATION

This is a continuation of International Application PCT/US00/19080, withan international filing date of Jul. 13, 2000, published in English.

TECHNICAL FIELD

The present invention relates to reaction mixtures that includeexothermic generating particles having a water soluble coating encasinga portion of the particles, a volatile component, and optionally, anaqueous solution, and a buffer. The reaction mixtures are especiallysuited to generate heat in a controllable manner. Volatile componentscan be controllably released to the surrounding environment by thepresent reaction mixtures. Apparatuses and methods that use thesereaction mixtures are also disclosed.

BACKGROUND OF THE INVENTION

There are many methods for delivering airborne components, such asfragrances, insect repellents and the like. Scented candles, forexample, are well know implements for delivering a desirable smell tothe air. Incense performs essentially the same function, but the aromais typically the natural smell evolved when the incense is burned. Thatis, incense typically does not require the addition of a fragrantcomponent, while scented candles are generally a mixture of wax and afragrance. In yet another variant of aroma delivering combustiondevices, candles have been used to heat liquids or gels causing avolatile component to evolve. Moreover, lamps that burn oil have beenused for ages, not only to provide light, but also to deliverfragrances. Combustion devices for delivering fragrances are well know,but most of these devices have also been used to deliver other airbornecomponents, such as insect repellents, medicinal vapors such aseucalyptus, and other compounds.

Unfortunately, combustion devices inherently give rise to safety issues.They can be accidentally knocked over resulting in a fire, or when leftunattended, many combustion devices can burn down to their base andignite the surrounding surface. Moreover, smoke is an inevitableby-product of any combustion device. In general, smoke from a combustiondevice can be noxious, and may cause long term health problems. Thus,while these devices are simple and inexpensive methods for deliveringairborne components, they are not without problems.

Another method of delivering airborne components is to simply rely onevaporation. For example, a liquid, solid or gel material that containsan airborne component can be placed anywhere and over time the airbornecomponent will evolve to the surrounding environment via evaporation.But this system relies on the difference between the vapor pressure ofthe airborne component and atmospheric pressure. If the vapor pressureof the airborne component is too high, the component will be deliveredto fast. Likewise, if the vapor pressure of the component is too low,the component will be delivered too slowly to make a marked effect inthe surrounding environment. Many insect repellents, for example, cannotbe delivered effectively by evaporation alone because of their highvapor pressure. Thus, evaporative devices are very limited in the typeof material they can deliver, and the speed with which these selectmaterials can be delivered.

Slightly more advanced apparatuses for delivering airborne componentsuse electrical power from batteries or an electrical outlet in the home.These devices typically use the electricity to provide heat, forced airflow, or both to speed the delivery of the airborne component.Unfortunately, these devices are necessarily more complicated andexpensive to build and operate than are combustion and evaporativedevices. While these devices may improve delivery, they increasecomplexity and cost. Moreover, the devices that are not battery operatedare inherently not portable as they require an electrical outlet.

Sprays and aerosols can deliver a wide variety of materials to the air.But these devices are, in general, manually operated and provide a shortburst of the delivered component. Sprays and aerosols are not wellsuited for the prolonged delivery of a substance unless they areprovided with a mechanical control mechanism. Such mechanical controlsare expensive and limit the portability of such devices.

Self contained exothermic reaction mixtures that are initiated by theaddition of an aqueous solution have been considered for deliveringcompositions to the surrounding air. A self contained exothermicreaction can provide heat without a combustion or an electrical source.The heat, in turn, can speed the evaporation of the composition that onewishes to deliver. As such, a wider range a compositions can bedelivered in this manner. But these reactions have one substantialproblem, they are hard to control. For example, it has been difficult todesign a reaction system that is self contained, and runs at a constanttemperature for an extended period of time. Likewise, it is difficult todesign a reaction system that will run at one temperature for a firstperiod of time, then change to a second temperature for a second periodof time. It is axiomatic that one cannot control the delivery of thedesired composition without controlling the temperature of the reactionsystem.

Thus, there exists a need for improved methods and apparatuses fordelivering compositions to the surrounding air. These improved methodsand apparatuses should overcome the problems discussed above.Specifically, they should not require combustion, and they should notrely solely on evaporation. There is a need for devices that delivercompositions to the air in a more controlled manner and for a longerperiod of time than aerosols and sprays. Moreover, these improvedmethods and apparatuses should be portable and relatively inexpensive.

SUMMARY OF THE INVENTION

The present invention is directed to a reaction mixture comprising thefollowing reaction components: exothermic generating particlescomprising a water soluble coating that encases a portion of theparticles; and a volatile component. Optionally, the reaction componentsfurther comprise an optional component selected from the groupconsisting of an aqueous solution, a buffer and mixtures thereof.

In one aspect of this invention the reaction components are mixedtogether, and the temperature of the reaction mixture increases to a SetTemperature that is greater than about 35° C. and less than about 75° C.within less than 20 minutes. More preferably, the reaction mixtureremains within 15° C. of the Set Temperature for at least about 45minutes.

The exothermic generating particles of the present invention arepreferably selected from the group consisting of uncomplexed metals,metal salts, metal oxides, metal hydroxides, metal hydrides and mixturesthereof. The metals are selected from the group consisting of beryllium,magnesium, lithium, sodium, calcium, potassium, iron, copper, zinc,aluminum and mixtures thereof. And the water soluble coating for theseexothermic generating particles comprises a water soluble materialpreferably selected from the group consisting of natural water-solublepolymers, inorganic water-soluble polymers, synthetic water-solublepolymers, semi-synthetic water-soluble polymers, polymers of plantorigin, polymers of microorganism origin, polymers of animal origin,starch polymers, cellulose polymers, alginate polymers, vinyl polymers,polyoxyethylene polymers, acrylate polymers, and mixtures thereof.

There is further provided in the present invention a process forgenerating heat comprising the steps of: providing exothermic generatingparticles comprising a water soluble coating that encases a portion ofthe particles; providing an aqueous solution and a volatile component;and adding to the coated exothermic generating particles the aqueoussolution and the volatile component.

In yet another aspect of this invention there is provided an apparatusfor generating heat comprising a container and the following reactioncomponents: exothermic generating particles comprising a water solublecoating that encases a portion of the particles; a volatile component;and an aqueous solution.

The methods and apparatuses of this invention provide portable andinexpensive ways to deliver compositions to the surrounding air in acontrollable manner. The devices can be relatively small while operatingin a controllable manner for an extended period of time. For example, areaction mixture can be designed to deliver a component to thesurrounding environment for an extended period of time at a relativelycontrolled rate. Moreover, using the reaction mixtures of the presentinvention a first component can be delivered to the air for a firstperiod of time, then the reaction mixture can automatically changetemperature to deliver a second component for a second period of time.

The apparatuses of this invention can be used to deliver a variety ofuseful compounds to the surrounding air, and to clothes, carpet, pets,skin and many other surfaces. Moreover, the apparatuses of thisinvention can be combined with color and light to improve the aestheticqualities, and ultimately, improve the overall experience for the userof the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the invention, it is believed that the inventionwill be better understood from the following description of preferredembodiments which is taken in conjunction with the accompanying drawingsin which:

FIG. 1 is a graphical representation of two controlled reactions with aSet Temperature of about 50° C. using reaction mixtures according to thepresent invention, and an uncontrolled reaction;

FIG. 2 is a graphical representation of two controlled reactions with aSet Temperature of about 40° C. using reaction mixtures according to thepresent invention, and an uncontrolled reaction; and

FIG. 3 is a schematic representation of an apparatus according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As noted, the present invention is directed to a reaction mixturecomprising the following reaction components: exothermic generatingparticles comprising a water soluble coating that encases a portion ofthe particles; and a volatile component. Optionally, the reactioncomponents further comprise a buffer, an aqueous solution, or both. Thereaction mixture can be used to generate heat in a controllable manner,which, in turn, assists in the evolution of the volatile component in acontrolled manner. Apparatuses that utilize the reaction mixtures taughtherein are also disclosed.

Reaction Mixture

In one aspect of this invention a reaction mixture is formed by mixingthe reaction components to initiate an exothermic reaction between theexothermic generating particles and the aqueous solution. The exothermicreaction generates heat, which elevates the temperature of the reactionmixture. The heat, more precisely, the elevated temperature of thereaction mixture, aides the evolution of the volatile component from thereaction mixture. As will be understood, the water soluble coating ofthe exothermic generating particles can be used to control the speed ofthe exothermic reaction, and the heat generated. The ability to controlthe amount of heat generated by the reaction mixture, without anyexternal controls, allows for the controlled delivery of the volatilecomponent.

As is well known to those skilled in the art, chemical reactions can bedifficult to control. Assuming a batch process, and putting asidethermodynamic considerations, the rate of an exothermic chemicalreaction depends largely on the temperature and concentration of thereaction mixture. With no external controls, the temperature of anexothermic reaction mixture will rapidly increase during the earlystages of the reaction. This is due largely to two factors, theconcentration of the reactants is at its highest level, and as thereaction progresses heat is generated which raises the temperature ofthe reaction mixture, which, in turn, increases the rate of thereaction. As the reactants are depleted, the reaction slows, causing aprecipitous decrease in the temperature of the reaction mixture. Thiseffect if graphically illustrated in both FIGS. 1 and 2, specifically,lines “A” and “a” illustrate the temperature of an uncontrolledexothermic reaction mixture as a function of time. FIGS. 1 and 2 arediscussed in greater detail below, but they clearly illustrate oneproblem addressed by the present invention. That is, the temperature ofthe reactions represented by Lines “A” and “a” of FIGS. 1 and 2,respectively, changes constantly. Moreover, the rate of change of thetemperature is almost never constant.

By coating the exothermic generating particles as described in detailbelow, a batch, exothermic reaction mixture can be designed to provideconstant heat over relatively long periods of time. And other controlschemes can be easily designed by those skilled in the art, for example,a reaction mixture can be designed where the temperature increasesgradually at a constant rate of increase for a relatively long period oftime. Other control schemes will be apparent based on the followingdetails.

In one such control scheme, a reaction mixture is prepared by mixing thereaction components to initiate an exothermic reaction. The temperatureof the reaction mixture increases to a Set Temperature that is greaterthan about 35° C. and less than about 75° C., preferably between about35° C. and 60° C., and most preferably between about 35° C. and 50° C.,within less than about 20 minutes, preferably within less than about 10minutes and more preferably within less than about 5 minutes.Preferably, the reaction mixture remains within 15° C., more preferablywithin 10° C., and even more preferably within 5° C. of the SetTemperature for at least about 45 minutes, preferably at least about 60minutes, and more preferably at least about 90 minutes. It is understoodthat the term “remains within” as used herein, means the same as “±”.For example, to “remain within 10° C.” of a Set Temperature of 50° C.,means the temperature can fluctuate between 40° C. and 60° C. Thiscontrol scheme is graphically illustrated in FIGS. 1 and 2 by Lines “B”,“C”, “b” and “c”.

FIG. 1 displays one “uncontrolled” exothermic reaction according to theprior art (“A”) compared to two “controlled” reactions according to thepresent invention (“B” and “C”). The reaction components, and theresulting reaction mixture are given in Table 1 and summarized in Table2. As can be seen, magnesium powder is used as the exothermic generatingparticles, and a citric acid buffer is used. The exothermic generatingparticles of reaction mixture “A” are uncoated (Premix 2), while theexothermic generating particles of reaction mixtures “B” and “C” includeboth uncoated particles (Premix 2), and particles coated withPolyethylene Glycol (“PEG”) of different molecular weights (Premix 1).The weight of the reactants (excluding the coating material) was heldconstant in these three reaction mixtures. That is, the weight of themagnesium exothermic generating particles and the citric acid buffer washeld relatively constant in all three reaction mixtures, see Table 2.Moreover, the magnesium exothermic generating particles and the citricacid buffer was added to 100.0 grams of water to form each of thereaction mixtures.

TABLE 1 A B C INGREDIENT Wt. % Wt. % Wt. % Premix 1 PEG 600 0.0 15.013.5 PEG 1000 0.0 5.0 4.5 Magnesium 0.0 5.0 4.5 Citric acid 0.0 32.529.3 Premix 2 Magnesium 13.3 5.7 6.4 Citric acid 86.7 36.8 41.8 TotalWt. % 100 100 100

TABLE 2 A B C INGREDIENT Wt. (g) Wt. (g) Wt. (g) Coating 0.0 4.8 4.3 Mg2.6 2.6 2.6 Citric Acid 16.6 16.6 17.1 Water Total Wt. (g) 19.2 24.024.0

As discussed briefly above, Line “A” is a typical graph of temperaturev. time for an uncontrolled exothermic reaction. The temperature risesrapidly at first to a maximum of greater than 65° C. And then, as thereaction components are consumed, the temperature begins to decreasealong a logarithmic curve. And within approximately 35 minutes, thereaction has cooled to within 5° C. of the initial temperature (roomtemperature). At no time during this first 35 minutes of the reactionillustrated by Line “A” does the temperature remain constant for morethan a few minutes.

In sharp contrast, the reaction mixtures represented by lines “B” and“C” of FIG. 1, increase to the Set Temperature of about 50° C. withinabout 10 minutes. The reaction temperatures then level off and remainwithin 5° C. of the Set Temperature for at least about 45 minutes.

Similarly, FIG. 2 displays one “uncontrolled” exothermic reactionaccording to the prior art (“a”) compared to two “controlled” reactionsaccording to the present invention (“b” and “c”). The reactioncomponents, and the resulting reaction mixture are given in Table 3 andsummarized in Table 4. Magnesium powder is used as the exothermicgenerating particles, and a citric acid buffer is used. The exothermicgenerating particles of reaction mixture “a” are uncoated (Premix 2),while the exothermic generating particles of reaction mixtures “b” and“c” include both uncoated particles (Premix 2), and particles coatedwith Polyethylene Glycol (“PEG”) of different molecular weights (Premix1). The weight of the reactants (excluding the coating material) washeld constant in these three reaction mixtures. That is weight of themagnesium exothermic generating particles and the citric acid buffer washeld relatively constant in all three reaction mixtures, see Table 4.Moreover, the magnesium exothermic generating particles and the citricacid buffer was added to 100.0 grams of water to form each of thereaction mixtures.

TABLE 3 a b c INGREDIENT Wt. % Wt. % Wt. % Premix 1 PEG 600 0.0 13.013.4 PEG 1000 0.0 21.3 22.0 PEG 2000 0.0 7.1 7.3 Magnesium 0.0 5.0 4.7Citric acid 0.0 32.3 30.5 Premix 2 Magnesium 13.3 2.8 2.9 Citric acid86.7 18.5 19.0 Total Wt. % 100 100 100

TABLE 4 a b c INGREDIENT Wt. (g) Wt. (g) Wt. (g) Coating 0.0 10.5 10.4Mg 2.0 2.0 1.9 Citric Acid 12.9 12.9 12.2 Total Wt. (g) 14.9 25.4 24.5

As discussed briefly above, Line “a” is a typical graph of temperaturev. time for an uncontrolled exothermic reaction. The temperature risesrapidly at first, and then as the reaction components are consumed, thetemperature begins to decrease along a logarithmic curve. It takesapproximately 15 minutes for the temperature of reaction mixture “a” toovershoot and cool back down to 55° C., which is within 15° C. of theSet temperature, 40° C. The reaction mixture remains within 15° C. of40° C. for only about 40 minutes later when the reaction dips below 25°C. At no time during this first 55 minutes of the reaction illustratedby Line “a” does the temperature remain constant for more than a fewminutes.

In sharp contrast, the reaction mixtures represented by lines “b” and“c” of FIG. 2, increase to the Set Temperature of about 40° C. withinabout 10 minutes. The reaction temperatures then level off and remainwithin 5° C. of the Set Temperature for at least about 60 minutes.

It is understood that the control scheme depicted in FIGS. 1 and 2, thatis, where the reaction mixture rises to a Set Temperature and thetemperature remains relatively constant for an extended period of time,is only one of many possible control schemes covered by the presentinvention. By way of example, another control scheme occurs when thereaction components are mixed together, the temperature of the reactionmixture increases to a First Set Temperature and remains within 15° C.,preferably within 10° C., and more preferably within 5° C. of the FirstSet Temperature for a first period of time and then moves to a SecondSet Temperature and remains within 15° C., preferably within 10° C., andmore preferably within 5° C. of the Second Set Temperature for a secondperiod of time. Preferably, the first period of time is at least about15 minutes, preferably at least about 20 minutes, and the second periodof time is at least about 15 minutes, preferably at least about 20minutes. And it is also preferred that the First Set Temperature be atleast about 10° C., preferably at least about 15° C., greater than theSecond Set Temperature, or alternatively, the First Set Temperature isat least about 10° C., preferably at least about 15° C., less than theSecond Set Temperature.

Yet another example of a control scheme of the present invention is whenthe reaction components are mixed together the temperature of thereaction mixture increases at an actual rate of increase that ismeasured in °C./minute, and the actual rate of increase remains within0.5° C./minute, preferably within 0.1° C./minute, and more preferablywithin 0.01° C./minute of a predetermined rate of increase for at leastabout 45 minutes, preferably at least about 60 minutes, and morepreferably at least about 90 minutes. Preferably the predetermined rateof increase is less than 2° C./minute, preferably less than 1.5°C./minute, and more preferably less than 1° C./minute.

Reaction Components

Turning now to the reaction components, which include as a minimum,exothermic generating particles comprising a water soluble coating thatencases a portion of the particles, and a volatile component.Preferably, the reaction components further comprise a buffer, and anaqueous solution, or both.

Exothermic Generating Particles

The exothermic generating particles of the present invention arepreferably selected from the group consisting of uncomplexed metals,metal salts, metal oxides, metal hydroxides, metal hydrides and mixturesthereof. The metals are selected from the group consisting of beryllium,magnesium, lithium, sodium, calcium, potassium, iron, copper, zinc,aluminum and mixtures thereof. These particles may also be selected fromthe group consisting of beryllium hydroxide, beryllium oxide, berylliumoxide monohydrate, lithium aluminum hydride, calcium oxide, calciumhydride, potassium oxide, magnesium chloride, magnesium sulfate,aluminum bromide, aluminum iodide, sodium tetraborate, sodium phosphateand mixtures thereof. The concentration of the exothermic generatingparticles in the reaction mixture is from about 3% to about 70%,preferably from about 5% to about 65%, and more preferably from about 8%to about 60%, by weight, of the reaction mixture.

It is preferred, although not required, that the exothermic generatingparticles (without the coating) have an average particle diameter offrom about 10 microns to about 1000 microns, preferably from about 100microns to about 500 microns, and more preferably from about 200 micronsto about 400 microns. In the present reaction mixture, the exothermicgenerating particles can be in the form of a dry powder, suspended in ahomogenous gel, or suspended in a non-aqueous solution.

Water Soluble Coating

Controlling the temperature of the reaction mixture as a function oftime is one of the objects of this invention, and control isaccomplished largely by coating at least a portion of the exothermicgenerating particles. While not wanting to be bound by any one theory,it is believed that the coated exothermic generating particles cannotreact with the aqueous solution until the coating dissolves. As thecoating on the exothermic generating particles begins to dissolve, theexposed particles begin to react and generate heat. In light of thismechanism, one can easily see the benefit of using a mixture ofexothermic generating particles have different coatings, differentthickness of coatings, or both. Likewise, it is often preferred toinclude a small amount of uncoated exothermic generating particles tohelp raise the temperature during the early stages of the reaction. Theconcentration of the water soluble coating material in the reactionmixture is from about 3% to about 70%, preferably from about 5% to about65%, and more preferably from about 8% to about 60%, by weight, of thereaction mixture.

Hence, it is understood that while a portion of the exothermicgenerating particles must be coated with the water soluble coatingsdisclosed herein, not all of the particles need to be coated. Moreover,some particles may have different thicknesses, and the coatings may bedifferent. More specifically, the exothermic generating particles can beselected from the group consisting of uncoated particles, coatedparticles and mixtures thereof, preferably, the exothermic generatingparticles comprise particles selected from the group consisting ofuncoated particles, first coated particles, second coated particles andmixtures thereof, wherein the first coated particle differ from thesecond coated particles in the coating material, the thickness of thecoating or both.

The coating for these exothermic generating particles should be a watersoluble material that is preferably selected from the group consistingof natural water-soluble polymers, inorganic water-soluble polymers,synthetic water-soluble polymers, semi-synthetic water-soluble polymers,polymers of plant origin, polymers of microorganism origin, polymers ofanimal origin, starch polymers, cellulose polymers, alginate polymers,vinyl polymers, polyoxyethylene polymers, acrylate polymers, andmixtures thereof. More specifically, the coating for the exothermicgenerating particles comprises a water soluble material selected fromthe group consisting of gum arabic, gum tragacanth, galactan, gum guar,carob-seed gum, karaya gum, carrageenan, pectin, agar, quince seed,alge-colloid, starch (from corn, potato, etc), glycyrrhizic acid, gumxanthan, dextran, succin-glucane, pullulan, collagen, casein, albumin,gelatin, carboxy-methyl starch, methyl-hydroxypropyl starch,methyl-cellulose, nitro-cellulose, ethyl-cellulose,methyl-hydroxypropyl-cellulose, hydroxy-ethyl-cellulose, sodiumcellulose sulfate, hydroxypropyl-cellulose, sodiumcarboxy-methyl-cellulose, crystalline cellulose, cellulose powder,sodium alginate, propylene glycol alginate ether, polyvinyl alcohol,poly (vinyl methyl ether), poly-vinyl-pyrrolidone, carboxy-vinylpolymers, alkyl co-polymers of acrylic acid and methacrylic acid,polyethylene glycol having a molecular weight between 200 and 100,000,preferably between 600 and 20,000, co-polymers of polyoxy-ethylene andpolyoxy-propylene, sodium poly-acrylate, poly ehtylacrylate, polyacrylamide, polyethylene imine, cationic polymers, bentonite, aluminummagnesium silicate, hectorite, silicic anhydride, and mixtures thereof.Preferably, the coating comprises a material selected from the groupconsisting of water-soluble alkylene glycols, water-soluble alcohols,and mixtures thereof. And even more preferably coating is not flammable.Exemplary coatings useful in the present invention are listed below inTable 5.

TABLE 5 Examples of natural Examples of semi-synthetic water-solublepolymers water-soluble polymers polymers of plant originstarch-related polymers gum arabic carboxy-methyl starch gum tragacanthmethyl-hydroxypropyl starch galactan cellulose-related polymers gum guarmethyl-cellulose carob-seed gum nitro-cellulose karaya gumethyl-cellulose carrageenan methyl-hydroxypropyl-cellulose pectinhydroxy-ethyl-cellulose agar sodium cellulose sulfate quince seedhydroxypropyl-cellulose alge-colloid sodium carboxy-methyl- starch (fromcorn, potato, etc.) cellulose glycyrrhizic acid cellulose, crystallinepolymers of microorganism origin cellulose, powder gum xanthanalginate-related polymers dextran sodium alginate succin-glucanepropylene glycol alginate ester pullulan polymers of animal origincollagen casein albumin gelatin Examples of synthetic examples ofinorganic water-soluble polymers water-soluble polymersvinyl-related polymers bentonite polyvinyl alcohol aluminum magnesiumsilicate poly (vinyl methyl ether) Laponite ® poly-vinyl-pyrrolidonehectorite carboxy-vinyl polymers silicic anhydride alkyl co-polymers ofacrylic acid & methacrylic acid polyoxyethylene-related polymers PEG 200PEG 600 PEG 1000 PEG 2000 PEG 4000 PEG 6000 PEG 20000 co-polymers ofpolyoxy-ethylene & polyoxy-propylene acrylate-related polymers sodiumpoly-acrylate poly ethylacrylate poly acrylamide polyethylene iminecationic polymers

As will be understood by those skilled in the art, the water solubilityof the coatings discussed above vary across a broad band. And ingeneral, the water solubility is dependent on temperature. Thus, tocontrol the temperature of a reaction mixture a skilled artisan caneasily select coatings that dissolve at the desired Set Temperature andvary the thickness of the coatings such that exothermic generatingparticles are exposed to the aqueous solution at various times. Anothermethod of control is to use different coatings that dissolve atdifferent rates. By this method, certain particles will be exposed earlyin the reaction, while other exothermic generating particles will takelonger to be exposed. Other methods of coating the exothermic generatingparticles to control an exothermic reaction will be apparent to thoseskilled in the chemical arts. It is understood that in any controlscheme, it may be preferred, although not necessary, to include someparticles that are not coated.

The coating can be applied to the exothermic generating particles by anyappropriate means. The easiest method is to soften or melt the coatingmaterial and mix it with the desired amount of exothermic generatingparticles. To achieve different coating thicknesses, separate batches ofparticles and coating materials can be prepared. For example, 100 g ofparticles can be mixed with 100 g of PEG 600, and separately, 100 g ofexothermic generating particles can be mixed with 200 g of PEG 600. Thetwo batches of particles can then be combined. The thickness of thecoating can be determined by a simple material balance using the averageparticle size of the exothermic generating particles and the amount ofcoating material added thereto. If a more precise measurement isdesired, spectroscopic analysis of the particles before and aftercoating can provide a very accurate particle size distribution.Spectroscopic particle size analyzers are well known.

While it is necessary to coat at least a portion of the exothermicgenerating particles of the reaction mixture, the volatile component,the optional buffer, and the other optional components, (discussedbelow) may or may not be coated. More specifically, the volatilecomponent, the optional buffer, and the other optional components, canbe coated along with the exothermic generating particles, they can becoated separately from the exothermic generating particles, or they canbe added without any coating. Combinations of these choices will alsoproduce acceptable results in many cases. Therefore, coating componentsother than the exothermic generating particles is the prerogative of theformulator.

Volatile Component

The reaction mixtures disclosed herein include as an essential componenta volatile component that is preferably selected from the groupconsisting of a perfume, a fragrance, an insect repellent, a fumigant, adisinfectant, a bactericide, an insecticide, a pesticide, a germicide,an acaricide, a sterilizer, a deodorizer, a fogging agent and mixturesthereof. The concentration of volatile component in the reaction mixtureis from about 0.01% to about 20%, preferably from about 0.1% to about15%, and more preferably from about 0.5% to about 10%, by weight, of thereaction mixture.

“Volatile component” as used herein means any compound that is evolvedfrom a reaction mixture according to the present invention to thesurrounding environment during an exothermic reaction. The term“volatile” does not imply any restrictions on the vapor pressure or theboiling point of the component. For example, many fine fragrances haveboiling points well above the boiling point of water, while otherfragrances have boiling points below water. Both types of fragrancesfall within the definition of “volatile components” if they are evolvedduring an exothermic reaction according to the present invention.Necessarily, however, the aqueous solution cannot be considered thevolatile component even though a portion of the aqueous solution mayevolve during the exothermic reaction.

Fragrances are preferred volatile components for use in the presentreaction mixture and preferred fragrances are selected from the groupconsisting of musk oil, civet, castreum, ambergris, plant perfumes,sandalwood oil, neroli oil, bergamot oil, lemon oil, lavender oil, sageoil, rosemary oil, peppermint oil, eucalyptus oil, menthol, camphor,verbena oil, citronella oil, cauout oil, salvia oil, clove oil,chamomille oil, sandalwood oil, costus oil, labdanum oil, broom extract,carrot seed extract, jasmine extract, minmosa extract, narcissusextract, olibanum, extract, rose extract, acetophenonene,dimethylinadane derivatives, naphthaline derivatives, allyl caprate,.alpha.-amylcinnamic aldehyde, anethole, anisaldehyde, benzyl acetate,benzyl alcohol, benzyl propionate, borneol, cinnamyl acetate, cinnamylalcohol, citral citronnellal, cumin aldehyde, cyclamen aldehyde,decanol, ethyl butyrate, ethyl caprate, ethyl cinnamate, ethyl vanillin,eugenol, geraniol, exenol, alpha.-hexylcinnamic aldehyde,hydroxycitrolnellal, indole, iso-amyl acetate, iso-amyl iso-valeratekiso-eugenol, linalol, linalyl acetate, p-methylacetophenone, methylanthranilate, methyl dihydroasmonate, methyl eugenol,methyl-.beta.-naphthol ketone, methylphenhlcarbinyl acetate, musk ketol,musk xylol, 2,5,6-nanodinol, gamma.-nanolactone,phenylacetoaldehydodimethyl acetate, beta.-phenylethyl alcohol,3,3,5-trimethylcyclohexanol, .gamma.-undecalactone, undecenal, vanillin,and mixtures thereof.

Aqueous Solution

An optional component of the present reaction mixtures is an aqueoussolution. The aqueous solution performs two functions in the reactionmixture. Specifically, it dissolves the water soluble coating on theexothermic particles and then reacts with the exothermic generatingparticles to generate heat. It is understood that the amount of theaqueous solution is quite flexible. While a sufficient amount of theaqueous solution must be present to dissolve the coating and to reactwith the exothermic particles, excess aqueous solution is oftenacceptable and may even be desirable. In fact, excess aqueous solutionacts as a heat sink for the reaction system. In this capacity theaqueous solution can, in some circumstances, be used to control themaximum temperature of a given reaction system. The aqueous solution,however, is generally not useful for controlling the time versestemperature curves for the reaction system as described above. Thus,those skilled in the art will be able to select the proper amount ofaqueous solution for a given reaction system.

The most common and most preferred aqueous solution is water andsolutions containing water. Monohydric alcohols and other low molecularweight liquids are suitable for use in the present invention. The onlycriteria for an “aqueous solution” is that it dissolve the water solublecoatings described above, and that it react with the chosen exothermicgenerating particles. The concentration of aqueous solution in thereaction mixture is from about 30% to about 97%, preferably from about50% to about 95%, and more preferably from about 60% to about 90%, byweight, of the reaction mixture.

Buffer

The reaction mixtures of the present invention will often include, as anoption component, a buffer. The buffer can provide a variety ofbenefits, such as acceleration or deceleration of the exothermicreaction, and pH control at the end of the reaction. It is well knownthat certain exothermic generating particles will react faster thanothers. A buffer can speed up or slow down a reaction mixture. It isunderstood, however, that even with a buffer, uncontrolled exothermicreactions will generally follow the time vs. temperature curves depictedin Lines “A” and “a” of FIGS. 1 and 2. Thus, the buffer works to providea favorable thermodynamic environment for the reaction mixture, but thebuffer does not control the time vs. temperature profile of thereaction. With regard to pH, it is often desirable to control the pHboth during the reaction and at the end of the reaction. During thereaction, the pH can contribute to the favorable thermodynamicenvironment as discussed above, and it can regulate the final pH of thereaction mixture when the exothermic reaction is nearing completion. Thefinal pH may be important because at certain pHs the reaction productswill precipitate leaving a relatively clear solution. The clear solutionmay be desirable and it can signal the end of the reaction. Regardless,a buffer may help the formulator of the reaction mixtures disclosedherein.

Preferably, if a buffer is present in the reaction mixtures of thisinvention, the ratio by weight of the exothermic generating particles tothe buffer is in the range of from 1000:1 to 1:1000, preferably from500:1 to 1:500, and more preferably from 200:1 to 1:200. And the bufferis preferably selected from the group consisting of citric acid, malic,acid, fumaric acid, succinic acid, tartaric acid, formic acid, aceticacid, propanoic acid, butyric acid, valeric acid, oxalic acid, malonicacid, glutaric acid, adipic acid, glycolic acid, aspartic acid, pimelicacid, maleic acid, phthalic acid, isophthalic acid, terphthalic acid,glutamic acid, lactic acid, hydroxyl acrylic acid, alpha hydroxylbutyric acid, glyceric acid, tartronic acid, salicylic acid, gallicacid, mandelic acid, tropic acid, ascorbic acid, gluconic acid, cinnamicacid, benzoic acid, phenylacetic acid, nicotinic acid, kainic acid,sorbic acid, pyrrolidone carboxylic acid, trimellitic acid, benzenesulfonic acid, toluene sulfonic acid, potassium dihydrogen phosphate,sodium hydrogen sulfite, sodium dihydrogen phosphate, potassium hydrogensulfite, sodium hydrogen pyrosulfite, acidic sodium hexametaphosphate,acidic sodium pyrophosphate, acidic potassium pyrophosphate, sulfamicacid, ortho-phosphoric acid, pyro-phosphoric acid and mixtures thereof.

Other Ingredients

The reaction mixtures of the present invention may comprise, as optionalcomponents, other ingredients. These optional ingredients can be, forexample, visual enhancement agents selected from the group consisting ofa dye, a chemiluminescence agent, a fluorescence agent, a pearlescenceagent, and mixtures thereof. More preferably, the visual enhancementagent is selected from the group consisting of fire-fly luciferase,adenosinetriphosphate, ethylene glycol disteacate and mixtures thereof.These visual enhancement agents can be used to color the reactionmixture, make it “glow”, or provide other visually satisfying effects.The concentration of in the other ingredients, if present in thereaction mixture is from about 0.01% to about 30%, preferably from about0.1% to about 20%, and more preferably from about 0.5% to about 15%, byweight, of the reaction mixture.

Apparatus

In yet another aspect of this invention there is provided an apparatusfor generating heat, the apparatus comprises a container and thefollowing reaction components: exothermic generating particlescomprising a water soluble coating that encases a portion of theparticles; a volatile component; and an aqueous solution. The apparatusoptionally further comprises a buffer. The reaction components for usein the apparatuses of the present invention are the same as thosediscussed above. The apparatus of the present invention is preferably aself contained and portable device in which an exothermic reaction isconducted. Preferably, the apparatus container should have at least onevent or opening to emit the volatile components that are evolved duringthe exothermic reaction. Moreover, the container should be constructedof a material that can withstand the maximum temperature of theexothermic reaction. Many materials fulfill this requirement because themaximum temperature of the reaction might be as low as 35° C., highertemperature reaction might require higher temperature tolerance. Glass,plastic, styrofoam, metal, liquid impermeable paper, and many othermaterials are suitable for use in the present invention. The containeris preferably clear, transparent, or translucent, although opaquecontainers, while less preferable, are suitable for use herein. In thepresent apparatuses, the exothermic generating particles can be in theform of a dry powder, suspended in a homogenous gel or suspended in anon-aqueous solution.

FIG. 3 is a schematic representation of an apparatus 10 according to thepresent invention. Apparatus 10 comprises container 12 and reactionmixture 20, which includes exothermic generating particles 22 withcoating 24. Reaction mixture 20 further comprises buffer particles 26and an aqueous solution 28. Volatile component 30 appears throughoutreaction mixture 20 as emulsified droplets, although volatile component30 can also be dissolved in aqueous solution 28 or incorporated intocoating 24. Container 12 sits on base 32 that houses light source 34 andpower source 36.

The reaction mixture used in the apparatuses of the present inventionshould be controllable as discussed above. That is, when the reactioncomponents are mixed together in the present apparatuses, the reactionmixture should increase in temperature to a Set Temperature that isgreater than about 35° C. and less than about 75° C., preferably betweenabout 35° C. and 60° C., and most preferably between about 35° C. and50° C., within less than about 20 minutes, preferably within less thanabout 10 minutes and more preferably within less than about 5 minutes.Preferably, the reaction mixture within the apparatus remains within 15°C. of the Set Temperature for at least about 45 minutes, preferably atleast about 60 minutes, and more preferably at least about 90 minutes.Other control sequences, such as those describe above in conjunctionwith the reaction mixture are contemplated for use in the presentapparatus.

In one preferred embodiment of the present invention, the apparatusincludes a light source. The light source, which can optionally providecolored light, can be used to enhance the visual effect of theapparatus. Moreover, as discussed above, visual enhancement agents maybe employed in the reaction mixture in addition to the light source. Thelight source can be used to accentuate the visual enhancement agents, orsimply to “light up” the apparatus. The light source can be batterypowered, solar powered or the like. While generally not preferred, thelight source could be externally powered by, for example, an electricaloutlet. The apparatuses of the present invention are preferablyportable, thus using external power may limit the portability. The lightsource can be within the container, or adjacent the exterior of thecontainer. If the light source is placed in the container, it will bepreferable to encase the light source and its power supply in a liquidimpermeable barrier to shield the device from the aqueous solution.Preferably, the container sits on a base that both supports thecontainer, and provides a housing for the light source.

The light source may contribute some heat to the reaction mixture, butthat is not the desired function. Moreover, most battery operateddevices operated at low voltage, and produce very little heat. Thus thelight source is not intended to function as a control mechanism.

One especially preferred light source for use in the present apparatusesis a light emitting diode (“LED”). LEDs are well known to the art andexamples of these devices can be found in, for example, U.S. Pat. No.5,963,185, which issued to Havel on Oct. 5, 1999, and U.S. Pat. No.5,940,683, which issued to Holm, et al. on Aug. 17, 1999. The entiredisclosure of the Havel and Holm et al. patents are incorporated hereinby reference. LEDs are small devices that provide numerous colors from asingle source. Thus, from one device, a variety of colors can beprojected onto the reaction mixture increasing the range of availablevisual effects. These devices have the additional benefit in that theyoperate at low power, and would require only a small battery or solarpower cell.

EXAMPLES

The following examples illustrate the reaction mixtures of the presentinvention, but are not necessarily meant to limit or otherwise definethe scope of the invention.

Method of Coating the Exothermic Generating Particles

-   Exothermic generating particles are coated with polyethylene glycol    as follows. A premix is made by combining magnesium powder and    anhydrous citric acid (1:6.5 w/w, both components from Wako    Chemicals), and then a fragrant oil is added to this premix. The    premix is then added into melted polyethylene glycol. The melted    polyethylene is a mixture of three different molecular weights, PEG    600 (from Union Carbide), PEG 1000 (from Wako Chemicals), and PEG    2000 (from Wako Chemicals). The melted PEG mixture is around 50° C.    The mixture is then cooled at 5° C. for 10 min to approximate    20–25° C. The product comprises PEG of three different molecular    weights, a fragrant oil, magnesium powder and anhydrous citric acid    powder, and is a gel with suspended particles.

1. A reaction mixture in the form of particles suspended in a gel or ina non-aqueous solution, comprising reaction components including: a)exothermic generating particles having an average particle diameter ofat least about 100 microns and comprising a water soluble coating thatencases a portion of the particles; and b) a volatile component,wherein, when the reaction components are mixed with an aqueous solutionto provide a resulting reaction mixture comprising from about 30 toabout 95% by weight of the aqueous solution, the resulting reactionmixture is operable to increase in temperature from about 20° C. to aset temperature that is greater than about 35° C. and less than about75° C., within less than about 20 minutes, and is operable to remainwithin 15° C. of the set temperature for at least about 45 minutes. 2.The reaction mixture of claim 1, wherein the exothermic generatingparticles are selected from the group consisting of uncomplexed metals,metal salts, metal oxides, metal hydroxides, metal hydrides and mixturesthereof, wherein the metals are selected from the group consisting ofberyllium, magnesium, lithium, sodium, calcium, potassium, iron, copper,zinc, aluminum and mixtures thereof.
 3. The reaction mixture of claim 1,wherein the coating comprises a water soluble material selected from thegroup consisting of natural water-soluble polymers, inorganicwater-soluble polymers, synthetic water-soluble polymers, semi-syntheticwater-soluble polymers, polymers of plant origin, polymers ofmicroorganism origin, polymers of animal origin, starch polymers,cellulose polymers, alginate polymers, vinyl polymers, polyoxyethylenepolymers, acrylate polymers, and mixtures thereof.
 4. The reactionmixture of claim 1, wherein the coating comprises a water solublematerial selected from the group consisting of gum arabic, gumtragacanth, galactan, gum guar, carob-seed gum, karaya gum, carrageenan,pectin, agar, quince seed, alge-colloid, starch, glycyrrhizic acid, gumxanthan, dextran, succin-glucane, pullulan, collagen, casein, albumin,gelatin, carboxy-methyl starch, methyl-hydroxypropyl starch,methyl-cellulose, nitro-cellulose, ethyl-cellulose,methyl-hydroxypropyl-cellulose, hydroxy-ethyl-cellulose, sodiumcellulose sulfate, hydroxypropyl-cellulose, sodiumcarboxy-methyl-cellulose, crystalline cellulose, cellulose powder,sodium alginaze, propylene glycol alginate ether, polyvinyl alcohol,poly (vinyl methyl ether), polyvinylpyrrolidone, carboxyvinyl polymers,alkyl co-polymers of acrylic acid and methacrylic acid, polyethyleneglycol having a molecular weight between 200 and 100,000, co-polymers ofpolyoxyethylene and polyoxy-propylene, sodium polyacrylate,polyethylacrylate, polyacrylarnide, polyethylene imine, cationicpolymers, bentonite, aluminum magnesium silicate, hectorite, silicicanhydride, and mixtures thereof.
 5. A process for delivering a volatilecompound to a surrounding environment, comprising adding water to thereaction mixture of claim
 1. 6. The process of claim 5, furthercomprising adding a buffer to the reaction mixture.
 7. The reactionmixture of claim 1, wherein the coating comprises polyethylene glycol.8. The reaction mixture of claim 7, wherein the polyethylene glycolcomprises a mixture of polyethylene glycols of varying molecularweights.
 9. The reaction mixture of claim 1, wherein the polyethyleneglycol has a molecular weight between 600 and 20,000.
 10. The reactionmixture of claim 1, wherein the exothermic generating particles have anaverage particle diameter of from about 100 microns to about 1,000microns.
 11. The reaction mixture of claim 10, wherein the exothermicgenerating particles have an average particle diameter of from about 100microns to about 500 microns.
 12. The reaction mixture of claim 10,wherein the exothermic generating particles have an average particlediameter of from about 200 microns to about 400 microns.
 13. Thereaction mixture of claim 1, wherein the volatile component is selectedfrom the group consisting of a perfume, a fragrance, an insectrepellent, a fumigant, a disinfectant, a bactericide, an insecticide, apesticide, a germicide, an acaricide, a sterilizer, a deodorizer, afogging agent and mixtures thereof.
 14. The reaction mixture of claim 1,wherein the reaction mixture is in the form of particles suspended in agel comprising polyethylene glycol.